This invention relates to systems and methods for processing substrates, such as magnetic disk substrates and optical disk substrates, and, more particularly, to systems and methods for processing substrates in vacuum. A modular construction may be used. Modular construction permits the addition of modules needed for a particular sequence of process steps, permits substrates to be maintained in vacuum throughout processing and permits processes to be isolated from each other. The invention also relates to a dual processing module which may operate in a serial mode or a parallel mode.
A typical magnetic disk used in a hard disk drive may include an underlayer of chrome, one or more magnetic layers for information storage and a protective layer, such as a carbon layer. The magnetic disk may also include a lubricant layer over the carbon layer to minimize friction and to facilitate handling of disks as well as functions during operations with the read-write head. The layers are generally formed on both front and back surfaces of a suitable substrate to provide a two-sided magnetic disk. The layers may also be formed on only one surface of the substrate. Sputter coating may be utilized for forming at least some of the layers of a magnetic disk. Different layers may be formed in different process stations of a multiple process station coating system. Coating systems of this type are disclosed, for example, in U.S. Pat. No. 5,215,420 issued Jun. 1, 1993 to Hughes et al. and are commercially available from Intevac, Inc. of Santa Clara, Calif. under Model Nos. MDP250B, MDP250B+ and MDP250K. Deposition techniques other than sputter coating may also be used at one or more of the process stations. Such other deposition techniques may be used in combination with sputtering processes, as well as other deposition processes.
The above-specified coating systems include multiple process stations mounted in a circular arrangement with respect to a circular main vacuum chamber. The process stations may include metal deposition stations, magnetic layer deposition stations, carbon deposition stations, heating stations and cooling stations in a desired sequence. The system may typically further include a mechanism for the handling of substrates moving into the system and transferring from process station to process station or from a cassette to the process stations and eventually back to the cassette.
One such coating system may include multiple process stations and has included as many as twelve process stations. In this system, grippers may be used to hold substrates, and in one commercial unit, substrates supported by grippers are raised into the respective process stations simultaneously. In such systems the process times in each station are necessarily equal. Accordingly, processes that require longer than the selected process time may utilize two or more process stations. For example, a substrate may warp if it is heated too rapidly, and therefore may be heated more slowly in two or more process stations.
As magnetic disks become more sophisticated and have higher recording densities, processing requirements become more exacting. For example, additional layers may be utilized to achieve enhanced performance. The additional layers require additional process stations and may require additional heating and/or cooling stations. In addition, contaminant levels must be reduced. As process requirements become more stringent, the requirement for high throughput is maintained or increased.
The coating systems described above provide highly satisfactory performance but have a fixed number of process stations and cannot easily be modified to add process stations. Furthermore, the substrates may be exposed to limited levels of contaminants in the main vacuum chamber. Although the process stations are typically isolated from the main vacuum chamber during processing, the process stations are in fluid communication with the main vacuum chamber when the substrates are being rotated to the next process stations. Certain processes, such as chemical vapor deposition used for carbon deposition, generate particles that may adversely affect other process steps or is the substrates. Although two or more separate sputter coating systems could be utilized to meet complex process requirements, it has generally been found desirable to maintain the substrates in vacuum throughout the entire sequence of process steps. For example, exposure of the substrate to atmosphere at an intermediate stage in the sequence of process steps, may result in contamination of the substrate surface, which may adversely affect subsequent process steps or the performance of the magnetic disk. Furthermore, the use of two or more independent coating systems to implement a single process sequence would be expensive.
Accordingly, there is a need for improved methods and apparatus for substrate processing which permit the addition of process steps for particular applications, which maintain the substrate in vacuum throughout the sequence of process steps, which achieve high throughput, and which are relatively low in cost.
According to a first aspect of the invention, a substrate processing system is provided. The substrate processing system comprises a primary processing assembly and one or more secondary processing assemblies. The primary processing assembly comprises a vacuum chamber for receiving a substrate holder containing multiple substrates, a plurality of process stations positioned to be fed from within the primary processing assembly are provided for individually processing substrates. There is also provided means for transporting the substrates to and between the process stations and the substrate holder. The secondary processing assembly comprises at least one secondary process station for processing the substrates. The substrate processing system may also further comprise a vacuum conveyor for transporting the substrate is holder in vacuum between the primary processing assembly and the secondary processing assembly, wherein the substrate holder containing substrates is maintained in vacuum during transport.
The substrate processing system may further comprise at least one vacuum lock between the primary processing assembly and the secondary processing assembly, so that, if desired, the primary processing assembly may be isolated by the vacuum lock from the secondary processing assembly.
The secondary processing assembly may include serial processing. modules, parallel processing modules and batch processing modules, singly or in any combination. In one embodiment, the secondary processing assembly comprises a dual processing module including a cassette vacuum chamber for receiving a substrate holder and first and second process stations coupled to the cassette vacuum chamber. The secondary processing assembly may further comprise a cooling module for cooling substrates processed in the primary processing assembly. The vacuum conveyor may comprise a vacuum chamber, a vacuum pump connected to the vacuum chamber and a conveyor for transporting the substrates or the holder for substrates through the vacuum chamber. In another embodiment, the vacuum conveyor comprises a rotation module, including a mechanism for changing the direction of transport of the substrates or the substrate holder in vacuum.
The secondary processing assembly may comprise one or more modules connected to an input of the primary processing assembly, one or more modules connected to the output of the primary processing assembly, or both. The modules may include processing modules, vacuum lock or isolation modules, vacuum conveyor modules, cooling modules and vacuum rotation modules, for example. The modules are interconnected to provide a desired system configuration.
According to another aspect of the invention, a dual processing module is provided. The dual processing module comprises a housing defining a vacuum chamber, first and second process stations coupled to the vacuum chamber, a conveyor for transporting a substrate or a holder containing substrates into and out of the vacuum chamber, a substrate positioning mechanism for raising or for lowering a substrate into and away from a processing chamber or into and our of a substrate holder, and first and second transfer mechanisms for transferring the substrates to and between a substrate lift mechanism and the first and second process stations.
The first and second transfer mechanisms may each comprise a turntable assembly for moving first and second substrate grippers between a load/unload position and a preprocess position, a transfer arm assembly for moving a substrate between the substrate lift mechanism and the load/unload position, and a gripper lift assembly for lifting one of the grippers between the preprocess position and a process position in the respective process station.
The dual processing module may include means for selectively operating in a serial mode or in a parallel mode. In the serial mode, each substrate is processed in both the first and second process stations. In the parallel mode, odd numbered substrates are processed in the first process station and even numbered substrates are processed in the second process station.